It has been proposed to grow plants on floating areas where the plants are supported on a flotation pad with their roots hanging into the water. However many difficulties and issues remain unsolved.
The following patents have been noted in this field: Japanese patent 9-29283 is an early attempt to treat water using a floating biomass.
U.S. Pat. No. 5,337,516 Hondulas is a land based system of high complexity where the roots hang in the water.
U.S. Pat. No. 6,322,699 Fernandez provides an arrangement in which waste water is treated using the general idea of using large plants grown on a floating mass with their roots hanging to clear water. The patent is not however filed in Canada.
US Published application 2012/0228216 Gavrieli is a recent application for a structure which floats and carries sheets on which microplants are carried. This uses agitation or aeration systems using power to drive them.
Published PCT application WO96/36568 discloses a method of extracting metals from water using hanging plants.
All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.
Plants suitable for the method herein can be of the type Typha, genus of about eleven species of monocotyledonous flowering plants in the family Typhaceae. The genus has a largely Northern Hemisphere distribution, but is essentially cosmopolitan, being found in a variety of wetland habitats. These plants are conspicuous and hence have many common names. They may be known as bulrush, or reedmace, and as cattail, catninetail, punks, or corn dog grass.
These plants grown in wetlands at the edges of lakes are known to carry out extraction of phosphates and other contaminants as these materials are taken up by the roots and thus absorbed into the plant. However this natural process has been lost due to the reduction in areas of wetland. Also the amount of phosphates and similar contaminants has much increased leading to a serious contamination of many lakes with the potential for environmental disasters.
In regard to one lake in Manitoba which is Lake Winnipeg, much of the emergent vegetation in the Netley-Libau Marsh has been lost over the past several decades. Consequently, any removal of the nutrients in the Red River that would formerly have been intercepted by those plants has also been lost. The water in much of the Netley-Libau Marsh is too deep (>1 meters) for plants to re-establish naturally.
Attempts have been made for new areas of growth to be established on artificial islands. However the construction of artificial islands for plant colonization in Netley-Libau Marsh would be costly and the investment would be lost if these islands are later found not to provide suitable habitat. If they do work, the practical use of vegetation growing on these islands would require the invention of amphibious equipment to harvest and transport the plants to land for processing (for biofuel and nutrient extraction benefits).